# A loudspeaker contains a coil of wire attached to a paper cone. The coil sits inside a permanent magnet. When an alternating current passes through the coil, the cone vibrates and produces sound. Explain why the cone moves backwards and forwards when an alternating current is used, rather than moving in only one direction.

> Eduqas GCSE Physics — 8.2 Magnetic effects of currents and the motor effect · Explain · 4 marks

> A loudspeaker uses the motor effect to convert electrical signals into sound. The coil of wire carrying a current sits within the magnetic field of a permanent magnet.

## Mark scheme (4 marks)

1. A current-carrying conductor in a magnetic field experiences a force (motor effect)
2. The direction of the force depends on the direction of the current
3. Alternating current continuously reverses direction
4. So the force on the coil/cone repeatedly reverses, causing it to vibrate / move back and forth

## Key terms

- [alternating current](https://www.gradenine.co.uk/glossary/alternating-current)

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-loudspeaker-contains-a-coil-of-fc6d0cbd) · Published by Druglandscape Ltd.